1. Field of the Invention
The present embodiment relates to a cam housing structure for a three-dimensional cam in which intake side supporting parts rotatably supporting an intake side camshaft from above and exhaust side supporting parts rotatably supporting an exhaust side camshaft from above are provided at upward of a cylinder head.
2. Description of the Related Art
Conventionally, an engine including a valve gear in which plural cylinders are disposed in parallel, a three-dimensional cam provided at a camshaft by each cylinder is slided in an axial direction in accordance with an acceleration opening degree to thereby continuously perform a variable control of a valve lift amount is known in engines of a motorcycle, a motor vehicle, and so on (for example, refer to Patent Document 1).
[Patent Document 1] Japanese Laid-open Patent Publication No. 2011-85051
In the valve gear including the three-dimensional cam as stated above, the three-dimensional cam slides on the camshaft, and therefore, it is necessary to enough increase stiffness and strength of a cam housing supporting the camshaft. However, there is a problem in which it is difficult to enough satisfy these requirements in the engine including the conventional valve gear.
Besides, there also is a problem in which it is difficult to secure paths to supply lubricant oil for the camshaft supporting the three-dimensional cam and a mechanism to drive the three-dimensional cam.